Exposure to beryllium dust causes a chronic lung disease, chronic beryllium disease (CBD), in some people. It may also cause beryllium sensitization, a reaction similar to an allergy. This sensitivity precedes the development of CBD. Once a person becomes sensitized to beryllium, he or she has cells in the blood or lungs capable of reacting to beryllium. These cells are the cause of the lung inflammation in CBD. The goals of the study Immunopathogenesis of Beryllium Disease are to better understand the ways in which cells of the immune system react to beryllium and to develop tests to measure beryllium allergy. Some individuals may have a genetic (inborn) susceptibility to develop beryllium sensitization. Studies have identified a genetic marker located on white blood cells, which is associated with chronic beryllium disease. The studies have not yet determined whether this marker alone identifies who will develop the disease. Our study is designed to try to determine what genetic markers control the allergic reaction to beryllium. Using a group of white blood cells called T-lymphocytes from the blood and lung, we are studying the relationship between the immune system response in CBD and a person's genetic make-up. Participation involves completion of a questionnaire regarding medical symptoms and work history; blood for immunologic and genetic laboratory studies; pulmonary function testing, exercise physiology testing and chest x-rays to determine disease progression; and bronchoalveolar lavage to determine disease progression and to obtain cells for immunologic and genetic laboratory studies. Participants are followed on an annual or biannual basis, depending on the severity of their disease.